Antennule shape and body size of Bosmina: key factors determining its vulnerability to predacious Copepoda

Abstract

Cyclopoid copepods are common in lakes and ponds, and they have a significant predation impact on the communities of the small zooplankton species. To reduce the predation risk, some cladoceran zooplankters develop protuberant (defensive) morphologies in the presence of the copepods. In the case of the small cladoceran Bosmina, they elongate their appendages (antennule and mucrone) and change the antennule morphotype. However, information about the effectiveness of these defensive devices against copepod predation is still insufficient. In our study, to find the compositive effects of these appendages on the vulnerability of Bosmina, we exposed two bosminid species (B. longirostris and B. fatalis) of different body sizes and with appendages of different lengths and shapes to copepod (Mesocyclops) predation. The experiment revealed that the shape of the antennule is a main factor determining the bosminid's vulnerability to copepod predation and indicated that the protection of the opened ventral carapace must be a key strategy by which Bosmina avoids copepod predation.

Proximate factors controlling the morphologic plasticity of Bosmina: linking artificial laboratory treatments and natural conditions

“…These results suggest that the individual death rate of B. longirostris due to copepod predation was not high, in agreement with the previous studies (Sakamoto & Hanazato, 2008). During our experiments, the dominant predator in the lake was the small Cyclopoida, Thermocyclops taihokuensis, while the density of Acanthocyclops vernalis was very low (Fig.…”

“…Recently, however, it has been found that the physical factors caused by mechanical attacks/handling by the copepods are additional cues enhancing the development of the anti-predator morphology in Bosmina longirostris: the ''cornuta''-morphed animals (hooked antennules) change their antennule shape to the ''pellucida''-morphotype (slightly curved antennules) (Sakamoto , 2007). The ''pellucida''-type antennules defend the bosminid's ventral opened carapace against copepod predation (Kappes & Sinsch, 2002;Chang & Hanazato, 2003;Sakamoto & Hanazato, 2008).…”

Size-selectivity of predatory reef fish on juvenile prey

“…These selective forces may act on a number of different body and performance characteristics, all of which can influence survival in a variety of situations. Such characteristics include body size (Allen 2008, Sakamoto & Hanazato 2008, overall condition (Husseman et al 2003, Penteriani et al 2008, growth rate (Takasuka et al 2003, Urban 2007, sensory development (Poling & Fuiman 1997) and escape speed (Brana 2003). Body size has by far received the most attention in the literature and is generally regarded as one of the major characteristics linked to survival during predatory encounters (Cohen et al 1993, Wellborn 1994, Sogard 1997, Wang et al 2007.…”

Multiple inducers in aquatic foodwebs: Counter-measures and vulnerability to exotics

“…Six of these predators, Limnocalanus , Leptodora , Mesocyclops , Acanthocyclops , Diacyclops , and Tropocyclops are now recognized to stimulate spine elongation directly in the laboratory (Kerfoot and McNaught ; this article). Studies by Sakamoto and Hanazato () also found induction in Bosmina stimulated by a variety of cyclopoid copepods: Mesocyclops , Acanthocyclops , and Thermocyclops .…”

“…Evidence for chemical specialization also comes from Japanese studies. In Lake Suwa, Japan, induction in B. longirostris was stimulated primarily by Mesocyclops , whereas induction in larger‐bodied Eubosmina fatalis was stimulated primarily by Leptodora (Chang and Hanazato ; Sakamoto and Hanazato ). In this case, the form of the mucro and antennule transformations differed markedly between the two prey taxa, making E. fatalis more susceptible to Mesocyclops predation.…”